Envelope tracking (ET) is a viable contender for next generation high efficiency radiofrequency (RF) power amplifiers (PA). One major challenge with ET is the timing alignment between the RF and envelope paths. Inaccurate alignment generates distortion which manifests itself as a degradation in the adjacent channel power ratio (ACPR) and error vector magnitude (EVM).
Complex calibration routines and hardware have been proposed to overcome this. This is acceptable in a high power transmitter, but for low power applications the excess power consumption and cost is a significant overhead.